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Aquatic invasive species have drastically changed how the San Francisco Estuary functions. During the past 2 decades, the effects of invasive species in the estuary may have increased in response to frequent and severe drought conditions. The invasive overbite clam (Potamocorbula amurensis), and the Asian clam (Corbicula fluminea) have well documented consequences on the estuarine food web, but their responses to drought are not well understood. Another invasive species, the jellyfish Maeotias marginata, can further affect the food web, but these effects have not been studied. We investigated the population responses of these invasive species to dry years and their potential effects on the pelagic food web using data from the Interagency Ecological Program’s monitoring surveys. We found M. marginata rapidly moves upstream with changing salinities during dry years, though it sees its highest abundance during high-outflow years in Suisun Bay and Suisun Marsh. Grazing rates of M. marginata in the estuary have not been quantified but are potentially high during localized blooms. The two invasive clams overlap in distribution, but have opposite population responses to drought conditions, with increases in P. amurensis densities and decreases in C. fluminea densities in dry years. With increasing P. amurensis densities, the clams’ combined annual filtration rates increase during drier years in the confluence and Suisun Marsh. Like M. marginata, P. amurensis also shifts upstream during droughts, but because adults cannot move immediately with a change in salinity, the population center of distribution shifts upstream the year after a dry year as a result of juvenile recruitment. If multiple dry years occur in a row, and both P. amurensis and M. marginata move upstream together, their effects on the food web could be compounded, and phytoplankton and zooplankton biomass could steeply decline in the confluence, affecting higher trophic levels in the estuary.

Environmental stressors such as land development and climate change impact biodiversity from local to landscape scales. Meta-ecosystem models can be used to represent these important cross-ecosystem interactions, but these models are rarely applied to real ecosystems. Here, we derive a meta-ecosystem model based on empirical data from the island of Newfoundland, Canada to predict how terrestrial disturbances will impact the functioning of small boreal streams. We study the effects of disturbances common in boreal systems: logging, insect outbreaks, unpaved roads, and general human impacts captured by the human impact index. We collect in situ data from 28 streams and analyze geospatial data at three spatial extents to inform the structure and analysis of our meta-ecosystem model. We use disturbance simulations in our meta-ecosystem model to identify mechanisms for how individual terrestrial disturbances affect streams. Top statistical models for our empirical data show that (1) benthic invertebrate biomass and specific conductivity increase with road density, (2) dissolved nitrogen and Ephemeroptera, Plecoptera, and Trichoptera (EPT) index increase with logging and insect outbreaks, and (3) benthic invertebrate biomass and percent shredders decrease with human impact index. Based on our boreal meta-ecosystem model simulations, logging may change the form of energy entering the aquatic ecosystem and weaken apparent competition between benthic invertebrates, periphyton, and leaf litter. Our unpaved road simulations suggest low sediment loading at our study streams increases habitat heterogeneity. Along with improving our mechanistic understanding of forest–stream ecosystems, our integration of empirical data and mathematical modeling creates a framework for using meta-ecosystem models to inform natural resource management. [ABSTRACT FROM AUTHOR]

Climate change is causing stream flow regimes to change in many regions globally, including southwestern Australia (SWA) where many perennial streams have switched to intermittent flow regimes. In drier landscapes, ecological refuges and evolutionary refugia will become critical for conserving freshwater biodiversity. This study aimed to determine the contribution of dry season refuges to species persistence and community recovery in a forested headwater catchment where perennial streams have been exposed to severe permanent drying, causing them to become intermittent. That is, in streams where formerly no drought refuges were present.Macroinvertebrate assemblages were sampled in dry season refuges within recently intermittent streams. Refuges included small spring‐fed pools, perched pools and subterranean refuges associated with granite inselbergs. Dry streambeds were searched for organisms aestivating in situ, and sediments were collected from each intermittent stream for rehydration.Mantel tests were used to compare the contribution of refuges to species assemblages in the early wet season when intermittent streams had begun to flow. Analysis of similarities was used to compare patterns between dry and wet season assemblages of intermittent streams and the single remaining perennial stream in the catchment, to infer the contribution of the perennial stream to community recovery in intermittent streams.Refuge types had very different assemblages: spring‐fed refuges supported several locally endemic species, but perched pools were dominated by opportunistic colonists. Several taxa were found aestivating in dry sediments, primarily adult Coleoptera and larval Chironomidae. Inselberg springs supported small populations of endemic Trichoptera and Ephemeroptera and provided subterranean refuge for an endemic amphipod. However, dry season refuges did not significantly contribute to community recovery. Rather, assemblages in early winter flows were similar to those inhabiting the perennial stream, showing that recolonisation from perennial streams is likely the primary process of community recovery in these recently intermittent streams.Newly formed dry season refuges supported some locally endemic species, but also colonising species that were formerly absent (or rare) when all streams were perennial. However, continued loss of perennial streams in SWA will result in landscape‐wide reductions in diversity (as colonisation sources are lost), because there are no known evolutionary refugia in this landscape for relictual species to retreat into. Granite inselbergs may become evolutionary refugia for a few species, as perennial streams are lost.Refuges will likely play a pivotal role in persistence of species able to use them; however, the existence of refuges is also under threat from prolonged climatic drying, including refuges newly formed by stream dry. Thus, identification and protection of future evolutionary refugia is a matter of urgency in regions facing drier climates, as it is ultimately evolutionary refugia that will become critical reservoirs of freshwater biodiversity as perennial streams and refuges are lost. [ABSTRACT FROM AUTHOR]

ABSTRACT Fishery discards worldwide increase the availability of organic materials on the benthos, altering trophic relationships and potentially increasing the abundance of benthic consumers. Expert knowledge from fishers is a valuable yet often underutilized source of information to understand these dynamics. We interviewed Dungeness crab fishers (n = 24) to determine the most‐used bait types and to characterize regional and seasonal bait use strategies that drive inputs of organic matter into Oregon coastal waters during the commercial Dungeness crab fishery each year. Based on bomb calorimetry measurements of caloric densities of 12 commonly reported bait species, total energetic input was 12.99 × 109 kJ (3.10 B kcal) from bait in the 2019–2020 commercial ocean Dungeness season in Oregon, USA. Fishing effort and bait inputs were strongly seasonal, with 88% of effort concentrated in the first 60 days of the 9‐month‐long season but did not vary regionally. This large, temporally concentrated caloric input suggested that bait could contribute substantially to Dungeness crab productivity. Fisher respondents indicated that bait effectiveness was the most important motivating factor in choosing a bait type, more than availability or cost. [ABSTRACT FROM AUTHOR]

(1) We investigated how local abiotic and biotic variables versus regional spatial and dispersal variables influenced the structure of a stream macroinvertebrate metacommunity (multiple assemblages linked by dispersal), and whether this varied by dispersal mode. (2) We collected 143 benthic macroinvertebrate samples and associated abiotic and biotic data related to local habitat and species interactions across three river basins on the Olympic Peninsula (Washington, USA). We assessed macroinvertebrate assemblage composition in relation to environmental and spatial variables using mixed effects linear regression and partial redundancy analysis. (3) We found that water temperature, substrate grain size, bankfull width, and salmonid density were the local factors significantly associated with macroinvertebrate assemblage composition. Local variables explained 19.7% of the variation in taxonomic composition, while overland spatial distance explained 7.4% (p = 0.014). Local variables were more important for aerially dispersing taxa than for aquatically dispersing taxa. (4) Our results indicated that local abiotic and biotic variables acted together with dispersal and overland distance to shape the macroinvertebrate metacommunity composition across river basins. The relative importance of local habitat variables and spatial processes depended on the dispersal mode, with evidence of dispersal limitation for aquatic dispersers. (5) Our study underscores the role of dispersal in influencing the effect of the local habitat on metacommunity organization, even at small spatial scales. We emphasize the need to apply metacommunity theory to stream management, such as incorporating distance between reaches and organismal dispersal traits in bioassessment models. [ABSTRACT FROM AUTHOR]

Epibenthic invertebrates in three estuaries of the Mekong River, namely Co Chien, Ba Lai, and Cua Dai, were sampled for ecological analysis in November 2022. The objectives of this research were to provide the first baseline survey of epibenthic communities in the Mekong estuaries and to describe more precisely the relationships between epibenthic characteristics and environmental parameters. In total, seven major taxa, including Bivalvia, Decapoda, Gastropoda, Isopoda, Molpadida, Stomatopoda, and Xiphosura were recorded in this estuarine system. The abundances of the epibenthic invertebrates range from 48 to 176 inds/1000 m2. Decapos always occupy the highest numbers with a percentage ranging from 86‒95%. There are 24 decapod species were recorded in this study with the following as dominant families Palaemonidae, Penaeidae, and Paguridae. Our findings highlight that the diversity of epibenthic communities, particularly for decapods, is notably high; however, the epibenthic density is considerably low. Epibenthic density and diversity were significantly correlated with salinity, TDS, depth, and pH but also other factors may play a role. The assessment of epibenthic assemblage diversity and its correlation with environmental factors holds significant importance in the formulation of conservation strategies. [ABSTRACT FROM AUTHOR]

Kelp forests support species-rich food webs that predator-prey interactions may sustain. Here, we analyze prey availability and stomach contents of the predatory fish Prolatilus jugularis in an unexplored subtidal kelp forest of Lessonia trabeculata in south-central Chile. In the kelp forest, 42 invertebrate taxa and 1016 individuals were observed. In the diet of P. jugularis, 21 taxa and 130 individuals were identified. Crustacea, particularly amphipods, were the dominant and more frequent taxa in the kelp forest and stomach contents. Annelida and Mollusca were also present in the kelp forest and diets but were less abundant. We did not find a statistically significant correlation between kelp forest and stomach-content prey abundances and frequencies. Also, dominance structure significantly differed between kelps and stomach contents. Our results indicate that P. jugularis could feed in other habitats outside the survey area. Seven predatory fish were sampled in the kelp forest. Pinguipes chilensis was the dominant fish, with 65% of the total fish biomass, followed by P. jugularis with 20%. [ABSTRACT FROM AUTHOR]

Results of the monitoring on the diversity and density of macrozoobenthos from the littoral zone of the locality Krani in Lake Prespa are presented. Three depths along three transects in this locality were sampled in spring and autumn of 2015. We recorded 25 taxa of macrozoobenthos belonging to eight classes: Turbellaria, Oligochaeta, Hirudinea, Gastropoda, Bivalvia, Amphipoda, Isopoda and Insecta. Seasonal changes (temperature, light availability, food availability and habitat conditions) as well as anthropogenic impacts affect macrozoobenthos communities. It was established that the density of communities is higher in autumn than in spring. Three species out of the 25 registered taxa were recorded with significantly higher densities: Dreissena carinata (14400 ind./m2), Gammarus triacanthus prespensis (4950 ind./m2) and Pyrgohydrobia prespaensis (4425 ind./m2). The results could contribute in obtaining a better understanding of the vertical and horizontal distribution, seasonal fluctuations in the population densities and the general state of the benthic fauna of this locality of high conservational importance. [ABSTRACT FROM AUTHOR]

Context: The rapid intensification of human impacts on rivers is a major threat for the provision of key ecosystem services for societies. In this context, many of these services rely on the ecological functions performed by macroinvertebrates. Therefore, understanding the relationship between human impacts and the functional diversity of macroinvertebrates is urgent. Aims: We aimed at analysing the relationship between human impact and the functional diversity of macroinvertebrates in rivers of agricultural lands of Argentina. Methods: We sampled seven rivers of central Argentina during three seasons (spring, autumn and winter). In each site, we measured pesticides, metals, chlorophyll- a , nutrients and the taxonomic and functional diversity of macroinvertebrates. We summarised the environmental information using principal-component analysis and assessed the relationship between the assemblage metrics with the first three principal components. Key results: We found that functional metrics presented a negative relationship with the human-impact gradient in the three seasons. However, taxonomic metrics showed less sensitivity. Conclusion: The functional diversity of macroinvertebrates, but not the taxonomic diversity, decreases with increasing human impacts on rivers. Implications: Our result implies that functional metrics should be included in environmental monitoring in agricultural lands of Argentina. We aimed at determining whether land use impairs the functional and taxonomic diversity of benthic macroinvertebrates in rivers in agricultural lands of Argentina. Functional diversity was more sensitive than taxonomic diversity to environmental stress. Our results highlighted the importance of including functional traits in environmental monitoring programs. [ABSTRACT FROM AUTHOR]

Benthic invertebrates play vital roles in estuarine ecosystems, but like other taxa they have been excluded from former marshlands by diking and land use conversion. Dike removal is one way of restoring marsh, but the response of benthic invertebrates has been little studied. Also understudied is variation in benthic invertebrate communities across entire deltas, particularly in the Pacific Northwest of North America where deltas receive high flows and sediment loads for their size. Our goals were to evaluate invertebrate response to large-scale dike removal on the Nisqually River Delta in Puget Sound, Washington, U.S.A., characterize delta-wide invertebrate community variation, and relate invertebrate response and spatial variation to environmental conditions. We sampled invertebrates annually from one year before to three years after dike removal in restoring marsh, previously restored marsh, undisturbed reference marsh, and adjacent tidal flats. Marine taxa immediately colonized the area recently restored to tidal inundation and population size grew exponentially thereafter for several of them. Community composition and diversity recovered completely, and density and biomass were approaching recovery three years later. Invertebrate communities converged between restoring and pre-existing marsh (previously restored and reference), suggesting an influence of reestablished connectivity. Just offshore from the dike line, invertebrates declined one year after dike removal but then rebounded indicating resilience to short-term disturbance. Dike removal effects were not detected farther offshore. Near the offshore edge of the delta, invertebrate biomass and body size were greater than elsewhere and a diverse assemblage of crustaceans, polychaetes, and bivalves was present. Farther inshore, tidal flats were dominated by a few species of small-bodied polychaetes and had higher density but lower biomass and diversity. Facultative detritivores, which can also filter feed, were the dominant feeding guild everywhere on the tidal flats. Density, biomass, diversity, and community composition on the marsh were more similar to the inner than outer tidal flats. Environmental variables most associated with invertebrate community variation were elevation, salinity, and sediment grain size and organic content. Our results are relevant to assessing performance and setting expectations for future restorations and have broad implications for the role of benthic invertebrates in estuarine ecosystems. [ABSTRACT FROM AUTHOR]

The presence of plastic particles in oceans has been recognized as a major environmental concern. The decrease in particle size increases their ability to directly interact with biota, with particles in the nanometer size range (nanoplastics—NPs) displaying a higher ability to penetrate biological membranes, which increases with the decrease in particle size. This study aimed to evaluate the role of life stages in the effects of poly(methyl)methacrylate (PMMA) NPs on the polychaete Hediste diversicolor, a key species in the marine food web and nutrient cycle. Thus, behavioral (burrowing activity in clean and spiked sediment) and biochemical endpoints (neurotransmission, energy reserves, antioxidant defenses, and oxidative damage) were assessed in juvenile and adult organisms after 10 days of exposure to spiked sediment (between 0.5 and 128 mg PMMA NPs/Kg sediment). Overall, the results show that H. diversicolor is sensitive to the presence of PMMA NPs. In juveniles, exposed organisms took longer to burrow in sediment, with significant differences from the controls being observed at all tested concentrations when the test was performed with clean sediment, whereas in PMMA NP-spiked sediment, effects were only found at the concentrations 8, 32, and 128 mg PMMA NPs/Kg sediment. Adults displayed lower sensitivity, with differences to controls being found, for both sediment types, at 8, 32, and 128 mg PMMA NPs/Kg sediment. In terms of Acetylcholinesterase, used as a marker of effects on neurotransmission, juveniles and adults displayed opposite trends, with exposed juveniles displaying increased activity (suggesting apoptosis), whereas in adults, overall decreased activity was found. Energy-related parameters revealed a generally similar pattern (increase in exposed organisms) and higher sensitivity in juveniles (significant effects even at the lower concentrations). NPs also demonstrated the ability to increase antioxidant defenses (higher in juveniles), with oxidative damage only being found in terms of protein carbonylation (all tested NPs conditions) in juveniles. Overall, the data reveal the potential of PMMA NPs to affect behavior and induce toxic effects in H. diversicolor, with greater effects in juveniles. [ABSTRACT FROM AUTHOR]

Comparisons among vegetated and unvegetated intertidal habitats have led to the paradigm that benthic fauna are more abundant and diverse in the former. Mangroves and their associated saltmarshes are the dominant vegetation type in intertidal zones of the Ajuruteua Peninsula, northern Brazil, however until now, there no studies that investigate the benthic fauna among vegetated and unvegetated intertidal habitats. Therefore, the present study compares the macrobenthic fauna among red mangrove (Rhizophora mangle), saltmarsh (Spartina alterniflora) and adjacent unvegetated sediment (mangrove borders and saltmarsh borders) in the Furo Grande tidal channel in the Caeté estuary, northern Brazil. Overall, vegetated habitats have finer sediments, lower salinities and temperatures and higher organic matter and water content than unvegetated habitats. However, the macrofauna structure among the habitats did not fully correspond to this division, perhaps responding instead to differences among the four habitats in detrital production, tidal inundation frequency, leaf litter processing by crabs and rates of predation. Deposit feeding tubificid oligochaetes and capitellid polychaetes were particularly abundant in the mangrove and at mangrove borders probably due to greater availability of suitably processed detritus. [ABSTRACT FROM AUTHOR]

Fish communities of streams and rivers might be substantially subsidized by terrestrial insects that fall into the water. Although such animal‐mediated fluxes are increasingly recognized, little is known about how anthropogenic perturbations may influence the strength of such exchanges. Intense land use, such as lignite mining, may impact a river ecosystem due to the flocculation of iron (III) oxides, thus altering food web dynamics. We compared sections of the Spree River in North‐East Germany that were greatly influenced by iron oxides with sections located downstream of a dam where passive remediation technologies are applied. Compared to locations downstream of the dam, the abundance of benthic macroinvertebrates at locations of high iron concentrations upstream of the dam was significantly reduced. Similarly, catch per unit effort of all fish was significantly higher in locations downstream of the dam compared to locations upstream of the dam, and the condition of juvenile and adult piscivorous pike Esox lucius was significantly lower in sections of high iron concentrations. Using an estimate of short‐term (i.e., metabarcoding of the gut content) as well as longer‐term (i.e., hydrogen stable isotopes) resource use, we could demonstrate that the three most abundant fish species, perch Perca fluviatilis, roach Rutilus rutilus, and bleak Alburnus alburnus, received higher contributions of terrestrial insects to their diet at locations of high iron concentration. In summary, lotic food webs upstream and downstream of the dam greatly differed in the overall structure with respect to the energy available for the highest tropic levels and the contribution of terrestrial insects to the diet of omnivorous fish. Therefore, human‐induced environmental perturbations, such as river damming and mining activities, represent strong pressures that can alter the flow of energy between aquatic and terrestrial systems, indicating a broad impact on the landscape level. [ABSTRACT FROM AUTHOR]

Dissolved organic matter (DOM), often measured as dissolved organic carbon (DOC), plays a fundamental role in influencing the structure and function of lake ecosystems. Due to the myriad ecosystem effects of DOM, widespread observations of long‐term increasing DOM concentrations have received much attention from ecologists. DOM positively influences primary production and consumer production at low concentrations due to the fertilising influence of bound nutrients. However, beyond a unimodal peak in production, a reduced light environment may result in a negative effect on production. This unimodal model has been largely developed and tested in lakes with low to moderate DOM concentrations (i.e., typically ≤10 mg/L DOC).To understand ecological responses in lakes across a larger range in DOM concentrations, we examined the response of benthic invertebrate communities in 148 Swedish lakes with DOM concentrations ranging between 0.67 and 32.77 mg/L DOC.We found that increasing DOM concentrations had a strong effect on invertebrate community composition below c. 10 mg/L. Across this range, abundances of individual taxa both increased and decreased, probably in response to environmental change induced by DOM. However, in lakes above this concentration, increasing DOM had minimal influence on community composition.As DOM concentrations continue to increase, faunal communities in lakes below this 10 mg/L DOC threshold are likely to undergo substantial change whereas those above this threshold are likely to be minimally impacted. [ABSTRACT FROM AUTHOR]

Land subsidence in intertidal environments may change the flooding regime and sediment composition, two drivers of the macrozoobenthic community. In the Dutch Wadden Sea, a UNESCO world heritage site, gas extraction has resulted in an average subsidence of intertidal mudflats of 2 mm year−1. These mudflats support an abundant macrozoobenthic community that offers important resources for birds and fish. The area is managed through the 'hand on the tap' principle, meaning that human activities should be halted if they affect the natural values. To what extent land subsidence affects sediment and macrozoobenthos remains unknown and is increasingly important given sea level rise.Taking advantage of a large‐scale monitoring program, we evaluated the effect of anthropogenically caused subsidence on sediment composition and macrozoobenthos. Nearly 4600 points were sampled yearly (2008–2020) across the Dutch Wadden Sea, allowing us to compare sediment composition and macrozoobenthos biomass within and outside the subsidence area while controlling for the main drivers of these variables. We also compared population trends within and outside the subsidence area for 31 species with different habitat use.Mud fraction was 3% higher within the subsided area and median grain size decreased at 1 μm year−1 while remaining constant in other mudflats. This had no effect on the total biomass of macrozoobenthos. Within the subsidence area, however, the biomass of species that use deeper areas increased compared to outside, and the opposite was true for species using shallower habitat.Policy implications: Land subsidence is related to changes in median grain size and macrozoobenthic community composition. However, because thresholds have not been defined, it is not clear if this requires management actions. For a successful implementation of the 'hand on the tap' principle in the Wadden Sea, it is necessary to define beforehand the relevant variables that represent the natural values, implement proper monitoring and define thresholds above which effects are not acceptable. We propose median grain size, mud fraction and macrozoobenthic composition as good measures of the natural values of the Wadden Sea, and the methods used here as a way for identifying anthropogenic effects on them. [ABSTRACT FROM AUTHOR]

Migratory shorebirds such as Calidris alba, C. fuscicollis, and Charadrius semipalmatus congregate in stopover areas like coastal wetlands to rest and feed, building up sufficient energy for their ongoing migration. To investigate the feeding ecology of these three shorebird species during their stopover, we conducted a comparative analysis of their feeding behavior and prey in Lagoa do Peixe National Park. We examined the feeding behavior using video recordings of 594 actively foraging individuals. Additionally, we determined the shorebirds' diet by analyzing 106 droppings collected from two areas within the park: the beach's intertidal zone and the lagoon's mudflats. The results highlighted that shorebird species showed marked differences in feeding strategies and prey captured during foraging. C. semipalmatus employed a visual-run-stop strategy with surface pecking, with no significant variations observed between the beach and the lagoon. The two Calidris species utilized a tactile-continuous hunting strategy, involving pecking and probing, with some variations observed between the beach and the lagoon. Multiple probing was mostly used on the beach, and single probing in the lagoon. The variation in probing behavior between the Calidris species appeared to be associated with differences in substrate type and food availability in the respective habitats they frequented. Additionally, our findings indicated that visual searching led to a more diverse prey selection, particularly in the lagoon. These differences in foraging strategies suggest that shorebird species can exploit the park's intertidal plains and trophic resources differently, emphasizing the importance of considering spatial and dietary variability in studying their foraging behavior. [ABSTRACT FROM AUTHOR]

The contribution of two basal energy sources - detrital organic matter and primary producers - as part of aquatic food webs varies typically along river continua. A host of barriers to river flow increase the water residence time and sediment and nutrient retention in reservoirs worldwide, and potentially alter the balance between detritus-based and algae-based energy pathways in the downstream food webs. We explored this issue on the Sélune River (Normandy, France), a small coastal stream that drains an agricultural catchment with high sediment runoff. Seasonal measurements of the following parameters were compared upstream and downstream of the reservoirs of two large dams (16 m and 36 m high): sediment fluxes, nutrient and chlorophyll a concentrations, algal communities in the epilithic biofilm (taxonomic composition, biomass and growth), and benthic invertebrate communities (abundance and trophic guild structure). As anticipated, annual sediment fluxes were much lower downstream of the reservoirs, where significant decreases in water turbidity, phosphate and silicate concentrations were recorded. A higher chlorophyll a concentration in water and a higher contribution of pelagic algae taxa to the photosynthetic biofilm suggested drifting and deposition of reservoir-borne phytoplankton downriver. Photosynthetic biofilm growth was higher downstream of the reservoirs in spring and fall, and so was the abundance of herbivores in the invertebrate community, notably scrapers and algae eaters. Energy pathways within riverine food webs were traced using stable isotope analyses of carbon (C) and nitrogen in the tissues of aquatic consumers (invertebrates and fish). Mixing models revealed a discontinuity in the origin of the C entering the food webs along the river continuum, confirming a greater contribution of algal C to aquatic consumers downstream of the reservoirs. These results illustrate mechanisms whereby large reservoirs can modulate C flow in food webs along a small coastal river with high sediment loads, and make it possible to anticipate the effects of dam removal on the future river ecosystem. [ABSTRACT FROM AUTHOR]

Important clues about the ecological effects of climate change can arise from understanding the influence of other Earth‐system processes on ecosystem dynamics but few studies span the inter‐decadal timescales required. We, therefore, examined how variation in annual weather patterns associated with the North Atlantic Oscillation (NAO) over four decades was linked to synchrony and stability in a metacommunity of stream invertebrates across multiple, contrasting headwaters in central Wales (UK). Prolonged warmer and wetter conditions during positive NAO winters appeared to synchronize variations in population and community composition among and within streams thereby reducing stability across levels of ecological organization. This climatically mediated synchronization occurred in all streams irrespective of acid–base status and land use, but was weaker where invertebrate communities were more functionally diverse. Wavelet linear models indicated that variation in the NAO explained up to 50% of overall synchrony in species abundances at a timescale of 4–6 years. The NAO appeared to affect ecological dynamics through local variations in temperature, precipitation and discharge, but increasing hydrochemical variability within sites during wetter winters might have contributed. Our findings illustrate how large‐scale climatic fluctuations generated over the North Atlantic can affect population persistence and dynamics in inland freshwater ecosystems in ways that transcend local catchment character. Protecting and restoring functional diversity in stream communities might increase their stability against warmer, wetter conditions that are analogues of ongoing climate change. Catchment management could also dampen impacts and provide options for climate change adaptation. [ABSTRACT FROM AUTHOR]

The objective of this work was to determine the taxonomic structure and Functional Feeding Groups (FFGs) of benthic invertebrates and their roles in two different water turbidity scenarios in a floodplain lake in the Pantanal wetland (Sinhá Mariana Lake, Barão de Melgaço, state of Mato Grosso). We studied the benthic invertebrate fauna at 18 sampling sites in periods of high turbidity (HT) and low turbidity (LT) during high water (HW) and low water (LW). We hypothesize that the structure of Chironomidae assemblages (species and functional feeding groups) varies between sites in Sinhá Mariana Lake, and the density and diversity attributes of species in this family and their functional feeding groups are reduced under increased turbidity. Depth, water temperature, turbidity, pH, pCO₂, water color, and organic matter content of the sediment were analyzed in each sampling site. Chironomidae presented higher density and diversity in periods of high water (HW) in sites with low turbidity water (LT). The dominance increased in periods of low water (LW). The main FFGs were represented by collector-gatherers, while the smallest groups corresponded to shredder-herbivores (50% and 9% of the total abundance, respectively). Collector-gatherers (Aedokritus sp., Chironomus strenzkei, Goeldichironomus petiolicola, G. maculatus, Beardius phytophilus), predators (Ablabesmyia gr. annulata, Labrundinia sp. and Cryptochironomus brasiliensis) and shredder-herbivores (Asheum sp., Polypedilum sp., Polypedilum gr. fallax) predominated in high water (HW) periods. A change in the community structure from the HW to LW was evidenced, characterized by the substitution of collector-gatherers for collector-filterers. Notodiaptomus deitersi (Crustacea) was dominant in LW (dominance index = 10.9) and Aedokritus sp. (Insecta) in HW (dominance index = 5.4). Water turbidity and the hydrological cycle are important factors determining spatial and temporal patterns in communities, particularly changes in FFGs. Changes in turbidity in different sites and periods alter the structure of trophic communities and lead to questions about the main drivers of communities in Pantanal wetlands as areas of high ecological relevance for maintaining biodiversity.

Benthic invertebrates play vital roles in estuarine ecosystems, but like other taxa they have been excluded from former marshlands by diking and land use conversion. Dike removal is one way of restoring marsh, but the response of benthic invertebrates has been little studied. Also understudied is variation in benthic invertebrate communities across entire deltas, particularly in the Pacific Northwest of North America where deltas receive high flows and sediment loads for their size. Our goals were to evaluate invertebrate response to large-scale dike removal on the Nisqually River Delta in Puget Sound, Washington, U.S.A., characterize delta-wide invertebrate community variation, and relate invertebrate response and spatial variation to environmental conditions. We sampled invertebrates annually from one year before to three years after dike removal in restoring marsh, previously restored marsh, undisturbed reference marsh, and adjacent tidal flats. Marine taxa immediately colonized the area recently restored to tidal inundation and population size grew exponentially thereafter for several of them. Community composition and diversity recovered completely, and density and biomass were approaching recovery three years later. Invertebrate communities converged between restoring and pre-existing marsh (previously restored and reference), suggesting an influence of reestablished connectivity. Just offshore from the dike line, invertebrates declined one year after dike removal but then rebounded indicating resilience to short-term disturbance. Dike removal effects were not detected farther offshore. Near the offshore edge of the delta, invertebrate biomass and body size were greater than elsewhere and a diverse assemblage of crustaceans, polychaetes, and bivalves was present. Farther inshore, tidal flats were dominated by a few species of small-bodied polychaetes and had higher density but lower biomass and diversity. Facultative detritivores, which can also filter feed, were the dominant feeding guild everywhere on the tidal flats. Density, biomass, diversity, and community composition on the marsh were more similar to the inner than outer tidal flats. Environmental variables most associated with invertebrate community variation were elevation, salinity, and sediment grain size and organic content. Our results are relevant to assessing performance and setting expectations for future restorations and have broad implications for the role of benthic invertebrates in estuarine ecosystems.

Abstract Drift or downstream dispersal is a fundamental process in the life cycle of many riverine organisms. In the face of rapidly declining freshwater biodiversity, there is a need to enhance our capacity to study the drift of riverine organisms, by overcoming the limitations of traditional labour‐intensive sampling methods that result in data of low temporal and spatial resolution. To address this need, we developed a new technology, the Riverine Organism Drift Imager (RODI), which combines in situ imaging with machine‐learning classification. This technique expands on the traditional methodology by replacing the collection cup of a drift net with a camera system that continuously images riverine organisms as they drift through the device. After being imaged, organisms are released into the environment unharmed. A machine‐learning classifier is used after field sampling to identify drifting organisms. Therefore, RODI provides a non‐invasive sampling method that can quantify organism drift at unprecedented temporal resolution. Multiple deployments have served to validate the performance of the technology in the field. In its current implementation, images are captured continuously for 1.5 h at 50 frames per second. We demonstrate that the quality of the resulting images enables a convolutional neural network classifier to identify organisms to the family level. The weighted F1 score, a metric for the performance of the classifier, was 94%, based on training and testing on a field‐collected dataset consisting of 4598 images of 285 organisms belonging to seven classes (one species, five families and one order). In conclusion, this work provides a proof of concept, demonstrating the viability of the deployment of RODI as an automated, in situ organism drift sampler. This novel approach offers the possibility to advance our fundamental understanding of the drift of riverine organisms and how this is affected by human impacts in natural streams while, at the same time, can serve as a cost‐effective tool for biodiversity monitoring.

Abstract Fish communities of streams and rivers might be substantially subsidized by terrestrial insects that fall into the water. Although such animal‐mediated fluxes are increasingly recognized, little is known about how anthropogenic perturbations may influence the strength of such exchanges. Intense land use, such as lignite mining, may impact a river ecosystem due to the flocculation of iron (III) oxides, thus altering food web dynamics. We compared sections of the Spree River in North‐East Germany that were greatly influenced by iron oxides with sections located downstream of a dam where passive remediation technologies are applied. Compared to locations downstream of the dam, the abundance of benthic macroinvertebrates at locations of high iron concentrations upstream of the dam was significantly reduced. Similarly, catch per unit effort of all fish was significantly higher in locations downstream of the dam compared to locations upstream of the dam, and the condition of juvenile and adult piscivorous pike Esox lucius was significantly lower in sections of high iron concentrations. Using an estimate of short‐term (i.e., metabarcoding of the gut content) as well as longer‐term (i.e., hydrogen stable isotopes) resource use, we could demonstrate that the three most abundant fish species, perch Perca fluviatilis, roach Rutilus rutilus, and bleak Alburnus alburnus, received higher contributions of terrestrial insects to their diet at locations of high iron concentration. In summary, lotic food webs upstream and downstream of the dam greatly differed in the overall structure with respect to the energy available for the highest tropic levels and the contribution of terrestrial insects to the diet of omnivorous fish. Therefore, human‐induced environmental perturbations, such as river damming and mining activities, represent strong pressures that can alter the flow of energy between aquatic and terrestrial systems, indicating a broad impact on the landscape level.

The contribution of two basal energy sources – detrital organic matter and primary producers – as part of aquatic food webs varies typically along river continua. A host of barriers to river flow increase the water residence time and sediment and nutrient retention in reservoirs worldwide, and potentially alter the balance between detritus-based and algae-based energy pathways in the downstream food webs. We explored this issue on the Sélune River (Normandy, France), a small coastal stream that drains an agricultural catchment with high sediment runoff. Seasonal measurements of the following parameters were compared upstream and downstream of the reservoirs of two large dams (16 m and 36 m high): sediment fluxes, nutrient and chlorophyll a concentrations, algal communities in the epilithic biofilm (taxonomic composition, biomass and growth), and benthic invertebrate communities (abundance and trophic guild structure). As anticipated, annual sediment fluxes were much lower downstream of the reservoirs, where significant decreases in water turbidity, phosphate and silicate concentrations were recorded. A higher chlorophyll a concentration in water and a higher contribution of pelagic algae taxa to the photosynthetic biofilm suggested drifting and deposition of reservoir-borne phytoplankton downriver. Photosynthetic biofilm growth was higher downstream of the reservoirs in spring and fall, and so was the abundance of herbivores in the invertebrate community, notably scrapers and algae eaters. Energy pathways within riverine food webs were traced using stable isotope analyses of carbon (C) and nitrogen in the tissues of aquatic consumers (invertebrates and fish). Mixing models revealed a discontinuity in the origin of the C entering the food webs along the river continuum, confirming a greater contribution of algal C to aquatic consumers downstream of the reservoirs. These results illustrate mechanisms whereby large reservoirs can modulate C flow in food webs along a small coastal river with high sediment loads, and make it possible to anticipate the effects of dam removal on the future river ecosystem.

This document is a corrigendum for a published manuscript that examines the structure and functional composition of macroinvertebrate communities in coastal plain streams across a precipitation gradient. The corrigendum addresses issues in the original manuscript, clarifying that only a portion of the collected data was analyzed due to a hurricane disturbance. The updated methods and results show the impact of the hurricane on the abundance and diversity of the macroinvertebrate communities. The study found that environmental factors such as rainfall, temperature, hydrological variables, and land cover variables were the main drivers of community composition. The authors acknowledge the potential influence of Hurricane Harvey on the results but conclude that the analyzed period represents typical dynamics in the study streams. The data from the study are available upon request. [Extracted from the article]

The arrival of a new invasive alga, Rugulopteryx okamurae, in the Strait of Gibraltar (SoG) in 2015 marked an unprecedented milestone in the North African and, later, in the European marine ecosystems. Nowadays, it is colonising vast infralittoral areas and significantly modifying some habitats and associated communities of the southern Iberian Peninsula. In recent expeditions, a high amount of free drifted thalli of this alga has been detected in different circalittoral and bathyal habitats of the northern SoG and the Alboran Sea. The present study combines quantitative data of this alga obtained with the use of a remotely operated vehicle (ROV) and a bottom otter trawl. The coverage–entanglement level of the drifted thalli on circalittoral and bathyal benthic invertebrates (e.g., not covering, covering only the basal part, covering one-third of the invertebrate, etc.) was also annotated from picture frames taken in locations with abundant drifted thalli. In underwater images, drifted thalli were mainly detected in circalittoral and bathyal bottoms of the northern SoG and the north-western Alboran Sea, between 50 to ca. 450 m depth. Nevertheless, abundant drifted thalli were also detected in bottom otter trawl samples from circalittoral bottoms of the north-central and north-eastern Alboran Sea. Small benthic organisms (e.g., encrusting sponges, hydrozoans, etc.) generally displayed low coverage–entanglement levels of drifted thalli. Nevertheless, large sessile and colonial benthic organisms with a complex three-dimensional morphology (e.g., gorgonians, colonial scleractinians) reached high levels of R. okamurae thalli entangled in different parts of their colonies. The drifted R. okamurae thalli entangled in these colonial suspension feeding organisms may hinder their feeding capability in the long term, resulting in habitat deterioration in the near future. [ABSTRACT FROM AUTHOR]

Lagoa do Peixe National Park (LP), in southern Brazil, is an important staging site for Red Knots (Calidris canutus rufa), especially during autumn migration. We describe the diet of Red Knots in LP by analyzing droppings and compare these findings with prey availability onsite. We collected droppings on a stretch of oceanic beach within LP in March and April 2006. We identified undigested prey items in 71 droppings, 32 collected in March and 39 in April. As expected, Red Knots at LP fed on abundant local benthic invertebrates. Beetles were present in almost all (95.7%) droppings. Other frequent items were mole crabs (Emerita brasiliensis), yellow clams (Mesodesma mactroides), and Argentinean wedge clams (Donax hanleyanus). The most abundant invertebrates in the lagoon were polychaetes and mud snails (Heleobia australis). On the beach, the most abundant invertebrates were polychaetes, isopods, and amphipods; however, mole crabs, yellow clams, and Argentinean wedge clams were also present in significant numbers. Prey availability coincides with Red Knot northward migration from Argentina: from January to April, small juvenile yellow and Argentinean wedge clams and mole crabs reach their highest quantities at LP. The high frequency of beetles in droppings was unexpected since nonbreeding Red Knots consume insects infrequently. According to the literature, beetles are the dominant benthic organisms on the backshore of beaches in southern Brazil. We speculate these insects are trapped by incoming tides, washed ashore, and captured by knots on the shoreline. O Parque Nacional da Lagoa do Peixe (LP), no sul do Brasil, é um importante local de parada para maçaricosde-peito-vermelho (Calidris canutus rufa), especialmente durante a migração de outono. Descrevemos a dieta do maçarico-de-peito-vermelho na LP por meio da análise de excrementos e comparamos esses resultados com a disponibilidade de presas no local. Coletamos fezes das aves em um trecho de praia oceânica na LP em março e abril de 2006. Identificamos partes não digeridas de presas em 71 excrementos, 32 coletados em março e 39 em abril. Como esperado, os maçaricos-de-peito-vermelho na LP se alimentaram de invertebrados bentônicos abundantes no local. Besouros estavam presentes em quase todos (95,7%) excrementos. As outras presas mais frequentes foram tatuíras (Emerita brasiliensis), mariscos-brancos (Mesodesma mactroides) e moçambiques (Donax hanleyanus). Os invertebrados mais abundantes na lagoa foram poliquetas e o gastrópode (Heleobia australis). Na praia, os invertebrados mais abundantes foram poliquetas, isópodes e anfípodes; no entanto, tatuíras, moluscos-brancos e moçambiques estavam presentes em números significativos. A disponibilidade de presas coincide com a migração para o norte dos maçaricos-de-peito-vermelho vindos da Argentina: de janeiro a abril, pequenos juvenis de mariscos-brancos e moçambiques e tatuíras atingem suas maiores quantidades na LP. A alta frequência de besouros nos excrementos foi inesperada, porque maçaricos-de-peito-vermelho consomem insetos infrequentemente durante o período não reprodutivo. Segundo a literatura, besouros são os organismos bentônicos dominantes no supralitoral de praias no sul do Brasil. Especulamos que esses insetos sejam capturados pela maré alta e levados até a zona entre marés e então consumidos pelos maçaricos-de-peito-vermelho. [ABSTRACT FROM AUTHOR]

Context: Improving our understanding of how riverine communities respond to anthropogenic change requires spatial comparisons across multiple sites, high-resolution temporal analyses, and examination of both taxa and trait responses. However, studies that encompass all these aspects remain scarce. Objectives: We used 10 years of annual monitoring data from 14 sampling sites in the Rhine-Main-Observatory (a Long-Term Ecological Research—LTER—site in Germany) to investigate spatiotemporal responses of stream macroinvertebrate communities along anthropogenic disturbance gradients (measured as 'ecological quality'). Methods: We examined spatiotemporal changes in various community components, including taxa, traits, metrics summarizing community responses (e.g., richness), and community composition. Results: Spatially, consistent patterns over a decade of sampling revealed that less-disturbed communities were characterized by higher taxonomic and trait diversity and occurrence of pollution-sensitive taxa. Anthropogenic disturbance tended to become less severe through time, particularly in more upstream sites, likely driven by improvements in land-use and water quality. Conversely, more downstream sites exhibited a lesser degree of improvement (or none at all) likely owing to persistent or cumulative stressors. Overall, taxonomic/trait metrics consistently reflected the magnitude of the environmental improvement, while community composition did not, suggesting a weaker link between community changes and anthropogenic impacts severity. Conclusion: Our results emphasize the importance of accounting for the variability in community responses to anthropogenic changes, and identifying optimal monitoring strategies to track such responses. In heterogeneous catchments, choosing which community component to focus and where to locate monitoring sites (e.g., monitoring ecological quality for the EU Water Framework Directive) can determine a timely detection of anthropogenic impacts. [ABSTRACT FROM AUTHOR]

There is a growing body of literature on the use of molecular methods for the ecological assessment of rivers based on benthic macroinvertebrates. Previous research has established the benefits of the use of environmental DNA (eDNA) to assess benthic macroinvertebrate communities as being more efficient, less subjective, and non-invasive compared to traditional methods. The aim of this review is to synthesize the existing knowledge on eDNA sampling, extraction, amplification and sequencing methods regarding river benthic macroinvertebrate metabarcoding studies. Literature searches were performed using two online databases, and following a screening process, 46 papers published between 2012 and 2022 met the eligibility criteria to be included in the review. Since the use of river macrobial eDNA in ecology is a fast-evolving field, the results showed that the methodologies used vary considerably among studies. A variety of filters are used for capturing eDNA from water or preservative ethanol and different sources of eDNA (i.e., sediment, biofilm) are also explored. This review identified 12 different extraction methods and 15 different primer pairs that were used more than once in benthic macroinvertebrate eDNA metabarcoding studies. Therefore, there is a need for standardization of some key steps of the eDNA metabarcoding process to increase the comparability of the results and the robustness of the methods for further implementation into large-scale monitoring programs. [ABSTRACT FROM AUTHOR]

Altering the hydrological connectivity between river channels and their riparian wetlands is a significant threat to river ecosystems. Aquatic insects are sensitive to environmental changes. In this study, community composition and functional traits of aquatic insects were investigated in reaches of the Manjiang and Songjiang Rivers, impacted by a water diversion project in northeast China. The species diversity of the flow-reduced reaches was more than twice as much as that of the reservoir riverine wetlands, and the species diversity of the flow-reduced reaches was less than twice as much as that of the natural riverine wetlands. Compared with the natural riverine wetlands, there was a lower abundance of scrapers in the reservoir wetlands, a higher abundance of filter collectors and shredders in the flow-reduced riverine wetlands, higher abundance of swimmers in the reservoir wetlands, and more sprawlers and swimmers in the flow-reduced wetlands. Co-occurrence network showed interspecific relationships of aquatic insect communities differed between the three types of riverine wetlands. Indicator species differed among wetland types. The environmental factors affecting the aquatic insect were water nitrate-nitrogen content, chlorophyll-a content, and electrical conductivity. In conclusion, proper hydrological connectivity between reaches wetlands should maintain to ensure ecological flow and biological connectivity. [ABSTRACT FROM AUTHOR]

Habitat quality and diversity strongly influence the composition of macroinvertebrate communities in lotic ecosystems. We evaluated the functional organization of macroinvertebrates in response to changes in habitat type and seasonality in the Afromontane Moiben River in western Kenya. In-stream substrate characteristics were evaluated at the reach, channel unit/habitat and microhabitat scales at nine sites in different land-use areas. Water and habitat quality were assessed during the dry (January–March) and wet (April–June) seasons. A total of 81 macroinvertebrate samples were collected every month from three channel units (pools, riffles and runs) defined by different substrate types and classified into five functional feeding groups (FFGs): collector-filterers, collector-gatherers, predators, scrapers and shredders. Numerical abundance differed significantly between FFGs, with gatherers > filterers > predators > scrapers > shredders. Coarse substrate (bedrock, boulders and cobbles) in riffles had the highest richness and abundance of filterers and scrapers while sand, mud and detritus in pools recorded the lowest richness and abundance. Shredders and scrapers occurred predominantly in upstream sites with minimal human disturbance, while gatherers were most abundant at disturbed sites. The greatest variability in FFGs was at the smallest microhabitat scale, and not at the reach scale. This study shows that attention should be given to both reach-scale and in-stream disturbances when assessing the ecological condition of streams and rivers. [ABSTRACT FROM AUTHOR]

We analyzed datasets from a long-term monitoring program of stream ecosystems in British Columbia, Canada, to determine whether or not it could detect climate change effects. In the Fraser River Basin (monitoring timespan 1994-2019), there was a marked (∼50%) increase in alpha diversity in reference streams, while BC North Coast (2004–2021) streams showed a modest trend of decreasing diversity and Columbia River Basin (2003–2018) and Vancouver Island (2001–2019) streams showed modestly increasing diversity. In all four regions, diversity across all sites in a specific period was primarily a function of sampling effort during this period rather than a temporal trend. Across all the regions, only three of 21 groups of faunally similar sites defined by Reference Condition Approach predictive modeling showed a suggestion of a directional change in community structure over time. Only 1 of 15 reference sites that were repeatedly sampled over several years showed a pattern that may indicate a response to changing climate. Three, not mutually exclusive, reasons why we did not see a clear effect of climate change on BC stream ecosystems were: 1) Little or no effect of climate change relative to other, potentially interacting biotic and abiotic factors, 2) The timespan of monitoring was too short to detect cumulative effects of climate change, and, most importantly, 3) The sampling design and protocol were unable to detect climate change effects. To better detect and characterize the effects of climate change on streams in monitoring programs, we recommend annual re-sampling of a few reference sites and detailed analysis of the natural and human environment of the sites along with better characterization of the benthic community (e.g. with eDNA) at all monitored sites. [ABSTRACT FROM AUTHOR]

The presence of plastic particles in oceans has been recognized as a major environmental concern. The decrease in particle size increases their ability to directly interact with biota, with particles in the nanometer size range (nanoplastics—NPs) displaying a higher ability to penetrate biological membranes, which increases with the decrease in particle size. This study aimed to evaluate the role of life stages in the effects of poly(methyl)methacrylate (PMMA) NPs on the polychaete Hediste diversicolor, a key species in the marine food web and nutrient cycle. Thus, behavioral (burrowing activity in clean and spiked sediment) and biochemical endpoints (neurotransmission, energy reserves, antioxidant defenses, and oxidative damage) were assessed in juvenile and adult organisms after 10 days of exposure to spiked sediment (between 0.5 and 128 mg PMMA NPs/Kg sediment). Overall, the results show that H. diversicolor is sensitive to the presence of PMMA NPs. In juveniles, exposed organisms took longer to burrow in sediment, with significant differences from the controls being observed at all tested concentrations when the test was performed with clean sediment, whereas in PMMA NP-spiked sediment, effects were only found at the concentrations 8, 32, and 128 mg PMMA NPs/Kg sediment. Adults displayed lower sensitivity, with differences to controls being found, for both sediment types, at 8, 32, and 128 mg PMMA NPs/Kg sediment. In terms of Acetylcholinesterase, used as a marker of effects on neurotransmission, juveniles and adults displayed opposite trends, with exposed juveniles displaying increased activity (suggesting apoptosis), whereas in adults, overall decreased activity was found. Energy-related parameters revealed a generally similar pattern (increase in exposed organisms) and higher sensitivity in juveniles (significant effects even at the lower concentrations). NPs also demonstrated the ability to increase antioxidant defenses (higher in juveniles), with oxidative damage only being found in terms of protein carbonylation (all tested NPs conditions) in juveniles. Overall, the data reveal the potential of PMMA NPs to affect behavior and induce toxic effects in H. diversicolor, with greater effects in juveniles.

The objective of this work was to determine the taxonomic structure and Functional Feeding Groups (FFGs) of benthic invertebrates and their roles in two different water turbidity scenarios in a floodplain lake in the Pantanal wetland (Sinhá Mariana Lake, Barão de Melgaço, state of Mato Grosso). We studied the benthic invertebrate fauna at 18 sampling sites in periods of high turbidity (HT) and low turbidity (LT) during high water (HW) and low water (LW). We hypothesize that the structure of Chironomidae assemblages (species and functional feeding groups) varies between sites in Sinhá Mariana Lake, and the density and diversity attributes of species in this family and their functional feeding groups are reduced under increased turbidity. Depth, water temperature, turbidity, pH, pCO₂, water color, and organic matter content of the sediment were analyzed in each sampling site. Chironomidae presented higher density and diversity in periods of high water (HW) in sites with low turbidity water (LT). The dominance increased in periods of low water (LW). The main FFGs were represented by collector-gatherers, while the smallest groups corresponded to shredder-herbivores (50% and 9% of the total abundance, respectively). Collector-gatherers (Aedokritus sp., Chironomus strenzkei, Goeldichironomus petiolicola, G. maculatus, Beardius phytophilus), predators (Ablabesmyia gr. annulata, Labrundinia sp. and Cryptochironomus brasiliensis) and shredder-herbivores (Asheum sp., Polypedilum sp., Polypedilum gr. fallax) predominated in high water (HW) periods. A change in the community structure from the HW to LW was evidenced, characterized by the substitution of collector-gatherers for collector-filterers. Notodiaptomus deitersi (Crustacea) was dominant in LW (dominance index = 10.9) and Aedokritus sp. (Insecta) in HW (dominance index = 5.4). Water turbidity and the hydrological cycle are important factors determining spatial and temporal patterns in communities, particularly changes in FFGs. Changes in turbidity in different sites and periods alter the structure of trophic communities and lead to questions about the main drivers of communities in Pantanal wetlands as areas of high ecological relevance for maintaining biodiversity.

Cape Rodney–Ōkakari Point Marine Reserve (North Island, New Zealand/ Te Ika-a-Māui, Aotearoa), is New Zealand's oldest marine reserve and includes one of the most visited beaches in the country. The reserve's effect on both target species and biogenic habitats is well-documented. It is less well-known, however, how protection affects other taxa. Here, we present two surveys, made nearly 50 years apart, of encrusting, intertidal bryozoans from Echinoderm Reef, quantify their relative abundance and species richness, and discuss possible reasons for the changes between 1971 and 2019. Prior to protection, encrusting bryozoans were common under boulders on Echinoderm Reef, a rocky intertidal mudstone terrace within the reserve. Since the reserve designation, however, there has been a decline in both abundance and species richness within this intertidal bryozoan community. Inconsistent sampling of the reserve's bryozoans makes it difficult to correlate changes in the bryozoan community with changes in the reserve's biotic and abiotic characteristics. Despite monitoring shortcomings, there is still value in the ad hoc biological surveys that have been performed, as they provide a snapshot of what communities were like at the time of collection. In the future, however, more research is needed to understand change within this bryozoan community. [ABSTRACT FROM AUTHOR]

Drift or downstream dispersal is a fundamental process in the life cycle of many riverine organisms. In the face of rapidly declining freshwater biodiversity, there is a need to enhance our capacity to study the drift of riverine organisms, by overcoming the limitations of traditional labour‐intensive sampling methods that result in data of low temporal and spatial resolution.To address this need, we developed a new technology, the Riverine Organism Drift Imager (RODI), which combines in situ imaging with machine‐learning classification. This technique expands on the traditional methodology by replacing the collection cup of a drift net with a camera system that continuously images riverine organisms as they drift through the device. After being imaged, organisms are released into the environment unharmed. A machine‐learning classifier is used after field sampling to identify drifting organisms. Therefore, RODI provides a non‐invasive sampling method that can quantify organism drift at unprecedented temporal resolution.Multiple deployments have served to validate the performance of the technology in the field. In its current implementation, images are captured continuously for 1.5 h at 50 frames per second. We demonstrate that the quality of the resulting images enables a convolutional neural network classifier to identify organisms to the family level. The weighted F1 score, a metric for the performance of the classifier, was 94%, based on training and testing on a field‐collected dataset consisting of 4598 images of 285 organisms belonging to seven classes (one species, five families and one order).In conclusion, this work provides a proof of concept, demonstrating the viability of the deployment of RODI as an automated, in situ organism drift sampler. This novel approach offers the possibility to advance our fundamental understanding of the drift of riverine organisms and how this is affected by human impacts in natural streams while, at the same time, can serve as a cost‐effective tool for biodiversity monitoring. [ABSTRACT FROM AUTHOR]

Early life stages are commonly thought to be highly sensitive to environmental contaminants and may offer insight into the future health of a population. Despite the importance of studying early life stages, very few standard protocols for benthic invertebrates commonly used in ecotoxicological assessments measure developmental endpoints. The goal of the present study was to develop and optimize a robust standard protocol for studying embryonic endpoints in freshwater gastropods. The developed method was then used to characterize the sensitivity of four embryonic endpoints (viability, hatching, deformities, and biomass production), in conjunction with juvenile and adult mortality, for the snail Planorbella pilsbryi exposed to three metals (copper [Cu], cadmium [Cd], and nickel [Ni]). Biomass production was typically the most sensitive endpoint but was relatively variable, while embryo hatching was slightly less sensitive but highly consistent for all three metals. However, no single embryonic endpoint was consistently the most sensitive, which demonstrates the importance of assessing a broad range of endpoints and life stages in ecotoxicological risk assessment. Interestingly, the embryonic life stage of P. pilsbryi was considerably less sensitive to Cu exposure compared with juvenile and adult mortality. However, for Cd exposure, embryonic endpoints were the most sensitive, and for Ni exposure, embryonic endpoints were similar in sensitivity to juvenile and adult mortality. The present study has valuable applications in conducting developmental toxicity research with organisms lacking standardized testing protocol as well as future applications in multigenerational and in silico toxicity research. Environ Toxicol Chem 2023;42:1791–1805. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. [ABSTRACT FROM AUTHOR]

The river–lake transitional zone provides a unique environment for the biological community and can reduce pollution inputs in lake ecosystems from their catchments. To explore environmental conditions with high purification potential in Lake Taihu and indicator species, we examined the river-to-lake changes in water and sediment quality and benthic invertebrate communities in the transitional zone of four regions. The spatial variations in the environment and invertebrate community observed in this study followed the previously reported patterns in Taihu; the northern and western regions were characterized by higher nutrient concentrations in water, higher heavy metal concentrations in sediment, and higher total invertebrate density and biomass dominated by pollution-tolerant oligochaetes and chironomids. Although nutrient concentrations were low and transparency was high in the eastern region, the taxon richness was the lowest there, which disagreed with the previous findings and might be due to a poor cover of macrophytes in this study. The river-to-lake change was large in the southern region for water quality and the invertebrate community. Water circulation induced by strong wind-wave actions in the lake sites of the southern region is assumed to have promoted photosynthetic and nutrient uptake activities and favored invertebrates that require well-aerated conditions such as polychaetes and burrowing crustaceans. Invertebrates usually adapted to brackish and saline environments are suggested to be indicators of a well-circulated environment with active biogeochemical processes and a less eutrophic state in Taihu, and wind-wave actions are key to maintaining such a community and natural purifying processes. [ABSTRACT FROM AUTHOR]

Organisms at the base of stream food webs are typically poor in long‐chain polyunsaturated fatty acids (LC‐PUFA), especially in docosahexaenoic acid (DHA), whereas consumers at higher trophic levels are often rich in LC‐PUFA. For example, fish tissues, especially the brain, are DHA‐rich. This obvious mismatch between consumer LC‐PUFA and their basal dietary supply may result from selective retention and/or endogenous conversion of dietary precursors to LC‐PUFA.To determine which is more likely, we investigated compound‐specific carbon stable isotopes in PUFA (δ13CPUFA) of potential basal resources (stream epilithon, leaf litter) and consumers (invertebrates, European bullhead, and two salmonid species and their brain, eye, liver, and muscle tissues). We predicted that consumer‐PUFA, depleted in 13C values relative to their dietary sources, would indicate internal de novo PUFA synthesis. Alternatively, higher consumer‐δ13CPUFA values would imply selective retention of aquatic (epilithon and conditioned leaves) rather than terrestrial resources or internal production, irrespective of trophic levels.Invertebrate grazers and predators resembled δ13C values of essential fatty acids (δ13CEFA) of benthic algae, while shredder‐δ13CEFA values reflected those of conditioned rather than fresh leaves. Lower eye‐δ13CEFA values of salmonids than in livers indicated high retention of dietary PUFA sources (invertebrates and epilithon). Stable isotope values of eicosapentaenoic acid suggest that all consumers retained algal EPA, while insectivorous fish produced DHA in their liver. There is no further evidence from carbon stable isotopes for local PUFA conversion within neural tissues.Our study demonstrates that δ13CPUFA can be used to track sources of these highly functional molecules in aquatic consumers and highlights the importance of algal derived‐PUFA for these consumers in oligotrophic headwater streams. [ABSTRACT FROM AUTHOR]

Aim: We studied molecular eukaryotic biodiversity patterns in shallow hard‐bottom Antarctic benthic communities using community DNA metabarcoding. Polar ecosystems are extremely exposed to climate change, and benthic macroinvertebrate communities have demonstrated rapid response to a range of natural and anthropogenic pressures. However, these rich and diverse ecosystems are poorly studied, revealing how little is known about the biodiversity of the Antarctic benthos associated with hard‐bottom habitats. Location: West Antarctic Peninsula and South Shetland Islands. Methods: Using data collected in seven localities along the western Antarctic Peninsula, we calculated spatial patterns of alpha and beta diversities. Furthermore, we analysed temporal changes in benthic composition in one location (Deception Island) over 3 years. We calculated the temporal alpha and beta diversities to reveal changes in this community over time. Results: We obtained a final list of 2057 molecular operational taxonomic units. We found significant differences in benthic community composition between localities and among years. Our dataset revealed a total of 10 different kingdom‐level lineages and 34 different phyla in the samples. The most diverse phylum was Arthropoda, followed by Bacillariophyta, and Annelida, while the highest relative read abundances belonged to Annelida, Porifera and Echinodermata. Benthic community compositions changed between 2016 and 2018 in Deception Island, and decreasing species richness was the main component of temporal beta diversity. Main Conclusions: Direct sampling methods are required for monitoring these complex communities. Informative biodiversity patterns can be retrieved even though most of the benthic biodiversity found in Antarctic habitats is yet to be taxonomically described and barcoded. Hard‐bottom assemblages exhibit high spatial variability and heterogeneity, not related to depth, which represent a huge challenge for large‐scale studies in the Southern Ocean. Local patchiness and structure within these communities are probably a consequence of a combination of several biotic and abiotic factors (i.e. ice disturbance, food supply and competition). [ABSTRACT FROM AUTHOR]

Human activities are the main cause of river pollution that continuously affect the water quality of the rivers. In this study, the population structure of macroinvertebrates was investigated as a biological indicator for water quality in the Khorram-rud River. For this purpose, a number of 4 stations were selected and some physicochemical parameters along with macroinvertebrates sampling were done monthly for 12 months (December 2018- November 2019) in each station. Totally 26 families in 14 orders of macroinvertebrates with the domination of families Chironomidae, Baetidae, and Tricorythidae, respectively were found. The results of physicochemical factors showed that the lowest and highest water temperatures recorded were 8.66 ± 0.57 in December and 23.66 ± 0.57 in July, respectively, the maximum average dissolved oxygen in March 5.83 ± 0.28 mg/l in the station (1), and the minimum was 0/00 mg/l in a station(4). pH value recorded with a minimum of 6 ± 0.86 in January and a maximum of 8 ± 0/00 in June. The average change of nitrite in different stations showed a slight fluctuation but was higher than the allowable limit in all stations. The highest amount of nitrate in a station (3) in June was 36.66 ± 5.77 and the lowest in a station (1) in December recorded as 2 ± 0/00 mg/l. The seasonal variations in density of macroinvertebrates indicate the maximum density in autumn and the minimum density in winter. The results based on (BMWP, ASPT) and richness and diversity indices (Shannon-Weiner, Margalef) indicated that the Khorram-rud river water is in the contaminated water class.

Acid rock drainage (ARD) impacts species composition in mountain streams. The potential impact for riparian birds experiencing elevated metal uptake by consumption of benthic invertebrates is concerning but not well studied. We investigated the influence of metal and rare earth element (REE) content in benthic invertebrates on the presence of breeding birds in an ARD-impacted watershed in Colorado, USA, where tree swallows in nest boxes had previously been found to have elevated metal concentrations at some sites. The concentrations of particular REEs in invertebrates were higher than those for cadmium or lead. Avian point counts indicated that most bird species detected were present at most sites, and that tree swallows were rarely found. Occupancy models showed that the availability of shrub or forest habitat was a good predictor for a few habitat-specialists, but metal and REE concentrations in water and invertebrates were not good predictors of avian presence. For other species, neither habitat type nor water quality were important predictors. Overall, this study indicates that the climate-change-driven increases in metals and REEs may not influence the presence of riparian birds in ARD-impacted streams. [ABSTRACT FROM AUTHOR]

Climate change is altering hydrological cycles globally, and in Mediterranean (med‐) climate regions it is causing the drying of river flow regimes, including the loss of perennial flows. Water regime exerts a strong influence over stream assemblages, which have developed over geological timeframes with the extant flow regime. Consequently, sudden drying in formerly perennial streams is expected to have large, negative impacts on stream fauna. We compared contemporary (2016/17) macroinvertebrate assemblages of formerly perennial streams that became intermittently flowing (since the early 2000s) to assemblages recorded in the same streams by a study conducted pre‐drying (1981/82) in the med‐climate region of southwestern Australia (the Wungong Brook catchment, SWA), using a multiple before‐after, control‐impact design. Assemblage composition in the stream reaches that remained perennial changed very little between the studies. In contrast, recent intermittency had a profound effect on species composition in streams impacted by drying, including the extirpation of nearly all Gondwanan relictual insect species. New species arriving at intermittent streams tended to be widespread, resilient species including desert‐adapted taxa. Intermittent streams also had distinct species assemblages, due in part to differences in their hydroperiods, allowing the establishment of distinct winter and summer assemblages in streams with longer‐lived pools. The remaining perennial stream is the only refuge for ancient Gondwanan relict species and the only place in the Wungong Brook catchment where many of these species still persist. The fauna of SWA upland streams is becoming homogenised with that of the wider Western Australian landscape, as drought‐tolerant, widespread species replace local endemics. Flow regime drying caused large, in situ alterations to stream assemblage composition and demonstrates the threat posed to relictual stream faunas in regions where climates are drying. [ABSTRACT FROM AUTHOR]

Inventories of biodiversity are crucial for helping support conservation and management efforts, yet the deep-sea, which is the largest biome on earth remains vastly understudied. Recent advances in molecular detection methods offer alternative techniques for studying inaccessible ecosystems, including those at depth. In this study we utilized environmental DNA metabarcoding, a first for studying deep-sea benthic environments in southern Africa, to assess biological diversity and to test the effects of depth and historical trawling activities on deep-sea communities. Utilising 29 sediment samples (thus focussing on predominantly meiofaunal and epifaunal biodiversity) and targeting a 313 bp region of the mtDNA cytochrome oxidase I gene, we recovered 444 OTUs across a wide array of species and genera. Even though many OTUs could only be assigned to higher taxonomic levels, results showed that biodiversity differed significantly across depth, suggesting that even at relatively small spatial scales (~ 6 km, across a depth gradient of 355 m to 515 m), eDNA derived biodiversity detected variation linked to the depth gradient. Comparison of the OTU database with known species inventories from the sampled area revealed little overlap, highlighting the need for expanding barcoding efforts of deep-sea species to aid future eDNA survey efforts. Overall our results suggest that within a South African context, increased barcoding efforts, in combination with eDNA metabarcoding and physical sampling could capture a greater proportion of benthic deep-sea biodiversity. This provides additional opportunities to underpin conservation and management decision-making in the region, such as evaluating potential sites for future protection. [ABSTRACT FROM AUTHOR]

Simons, A.L.; Aulerich, N.; Carlson, H.; Chandra, I.; Chancellor, J.; Gemayel, G.; Gillett, D.J.; Levene, D.; Line, J.; Nichol, G.; Patel, H., and Zhu, S., 2023. Using zeta diversity in describing the health of soft sediment benthic macroinvertebrates in the Southern California Bight. Journal of Coastal Research, 39(3), 418–430. Charlotte (North Carolina), ISSN 0749-0208. Ecological assessments of marine sediments have often focused on measures derived from the taxonomic, and sometimes functional, diversity of individual assemblages of benthic macroinvertebrates (BMIs). These assemblages are linked by a variety of ecological processes, demonstrating a need to describe groupings of them using regional measures of diversity. Here the use of zeta diversity is demonstrated, as a novel generalization of diversity measures, in assessing the health of regional groupings of BMI assemblages in the sediments of nearshore habitats such as estuaries and embayments. Using 1203 samples of BMI assemblages found in Southern California Bight (SCB), a model was constructed using three orders of zeta diversity, which accounted for up to 86% of regional variation in the mean health of assemblages, as described by the Benthic Response Index. Also investigated was the use of zeta diversity in assessing the relative likelihood of models of community assembly for regional groupings of BMIs, with niche assembly found to be likelier in both nearshore and offshore habitats. [ABSTRACT FROM AUTHOR]

Dichlorodiphenyltrichloroethane (DDT) contamination in the Toce River in northern Italy was studied by collecting data from 2016 to 2021 upstream and downstream of a production factory which in the past had discharged technical DDT. Analysis of sediments and of bioaccumulation in different benthic invertebrate taxa (Gammaridae, Diptera, Ephemeroptera Baetidae and Heptageniidae) was carried out to assess the transfer of DDT from sediments to benthic invertebrates and the environmental risk of this legacy pollutant for the river ecosystem. DDT and its metabolites dichlorodiphenyldichloroethylene (DDE) and dichlorodiphenyldichloroethane (DDD), here called DDx, were analyzed by isotope dilution gas chromatography–mass spectrometry (GC-MS/MS). DDx values in sediments in upstream stations (1.14–2.25 ng g−1 1% Organic Carbon) were lower than downstream of the industrial site (5.60–7.60 ng g−1 1% Organic Carbon), often exceeding Sediment Quality Guidelines for total DDx. Peak levels derived from new inputs of parental DDT, as confirmed by fingerprint analysis. Bioaccumulation was higher at downstream sites (up to 5107 ng g−1 lipid weight), confirming the bioavailability of residual DDT as well as active metabolism, with the formation of DDD and DDE. The Biota-Sediment Accumulation Factor evidenced the highest values (over 4.2) for Diptera and Gammaridae, highlighting that invertebrates can transfer contamination from sediments to the trophic chain. Linear regression models were developed to estimate DDx concentrations in benthic invertebrates from DDx concentrations in sediments. However, determination coefficients R2 remained in the range of 0.36–0.51, highlighting the necessity of bioaccumulation analysis to fully estimate environmental risk. The results show that DDT contamination, even if residual, may still represent a risk due to its effective transfer to the trophic chain. [ABSTRACT FROM AUTHOR]

Recent data suggests a significant difference in physical and biological properties between low-mountain lakes and high-mountain or lowland water bodies. However, the taxonomic composition and structure of bottom invertebrates in low-mountain lakes of Altai remain unknown. Due to climate change and growing anthropogenic impact, studying the composition and structure of macrozoobenthos in these lakes is becoming increasingly urgent. In 2022, a study was conducted on macrozoobenthos from foothill lakes of the Russian Altai, specifically Kireevo in the Krasnogorsk region, Aya (Aiskoye) in the Altai region, Koksha and Svetloye in the Soviet region, Kolyvanskoye in the Zmeinogorsk region, and Beloye in the Kuryinsky region of Altai Krai. The study identified 152 species from 9 classes, including Turbellaria (1), Nematoda (1), Oligochaeta (17), Hirudinea (5), Bivalvia (2), Gastropoda (8), Arachnida (10), Crustacea (2), and Insecta (106). Of the insects, the order Diptera (69 species, including 59 chironomids) had the greatest species diversity. Additionally, the orders Trichoptera (16), Coleoptera (7), Ephemeroptera (5), Odonata (4), Heteroptera (4), and Megaloptera (1) were identified. Most of the studied lakes in the Russian Altai (Aya, Beloye, Kireevo, and Kolyvanskoye) had a taxonomic composition of macrozoobenthos similar to lowland lakes. Two lakes (Koksha and Svetloye) had a combination of features from both lowland and high-mountain lakes. The content of organic substances and their decomposition products in water, as well as substrate type, were the most significant factors determining the development of macroinvertebrate communities in the studied lakes.

Synthetic pyrethroid (SP) insecticides are used extensively around the world in both agricultural and non-agricultural applications. Their toxicity to mammals is low, however, they have a high toxicity to invertebrates, fish and amphibians, including threatened species, affecting the health of the ecosystems and their biodiversity. This paper reviews the current global research on SP toxicity on non-target aquatic organisms and looks at the current biomonitoring approaches to detect their effects on aquatic ecosystems. Over the past decade, the toxicological effects of SPs on aquatic macroinvertebrates have been documented in laboratory, mesocosm and field studies. Toxicity of SPs for aquatic organisms can vary greatly between species and highlights the importance of assessing toxicity in all major aquatic groups. However, little data exist, and more research is needed on how sediment bound SPs affect less studied aquatic groups like zooplankton, amphibians and fish. Detecting stress caused by toxicants in aquatic ecosystems can indicate how SPs are affecting individual organisms and the community. Development of toxicity thresholds for all aquatic groups like invertebrates, fish and amphibians, should assist in assessing the biological risks of SPs to inform regulations and management actions to protect aquatic ecosystems.

The invasive seaweed Rugulopteryx okamurae has recently arrived in Europe from the western Pacific. Its explosive spread on coastal areas of the Gulf of Cádiz (GoC), Strait of Gibraltar and Alboran Sea is spoiling native coastal ecosystems and inflicting heavy losses on ecosystem services. We discovered for the first time large amounts (up to 17 g m–2) of detached R. okamurae thalli on deep-sea bottoms of the GoC that are being dragged from the Strait of Gibraltar shores into the NE Atlantic by the Mediterranean Outflow Water (MOW). Laboratory experiments revealed that collected unattached macroalgae from deep-sea locations were alive and healthy and maintained intact photosynthetic capacity after long dark periods, suggesting a tremendous resilience and invasive potential. Given the rapid transport of healthy thalli by the MOW and massive accumulation of them in the GoC basin, R. okamurae could represent a major threat to NE Atlantic ecosystems, affecting not only coastal but also deep-sea habitats. [ABSTRACT FROM AUTHOR]

Background: Benthic invertebrate (BI) surveys have been widely used to characterize freshwater environmental quality but can be challenging to implement at desired spatial scales and frequency. Environmental DNA (eDNA) allows an alternative BI survey approach, one that can potentially be implemented more rapidly and cheaply than traditional methods. Methods: We evaluated eDNA analogs of BI metrics in the Potomac River watershed of the eastern United States. We first compared arthropod diversity detected with primers targeting mitochondrial 16S (mt16S) and cytochrome c oxidase 1 (cox1 or COI) loci to that detected by manual surveys conducted in parallel. We then evaluated spatial and temporal variation in arthropod diversity metrics with repeated sampling in three focal parks. We also investigated technical factors such as filter type used to capture eDNA and PCR inhibition treatment. Results: Our results indicate that genus-level assessment of eDNA compositions is achievable at both loci with modest technical noise, although database gaps remain substantial at mt16S for regional taxa. While the specific taxa identified by eDNA did not strongly overlap with paired manual surveys, some metrics derived from eDNA compositions were rank-correlated with previously derived biological indices of environmental quality. Repeated sampling revealed statistical differences between high- and low-quality sites based on taxonomic diversity, functional diversity, and tolerance scores weighted by taxon proportions in transformed counts. We conclude that eDNA compositions are efficient and informative of stream condition. Further development and validation of scoring schemes analogous to commonly used biological indices should allow increased application of the approach to management needs. [ABSTRACT FROM AUTHOR]